Today, preservation of the global environment is being called for worldwide, and restrictions on emissions of greenhouses gases are becoming realized, centered on global warming prevention conferences. In such circumstances, it is desirable to reduce power consumption in image forming devices such as printer equipment, copy machines and the like as well.
In the past, so-called sleep control processing has been accomplished wherein power consumption is reduced by turning off the fixing heater when no printing commands are received by the image forming device from host equipment or the like for a set time. Image forming devices have also been proposed which reduce power consumption by switching the image exposure unit, operation display unit and so forth to low power consumption mode.
FIG. 12 is a flowchart showing one example of a power consumption control process in the image exposure unit executed by an image forming device that can set the image exposure unit to a low power consumption mode (hereafter referred to as a sleep mode). First, when the device power is turned on, as a preparatory step to the image forming process action, the image forming device sends light amount correction data to the image exposure units for each color (step (hereafter abbreviated ST) 91). This is a process that sends light amount correction data used in correcting variances in the flash light amounts among LED elements in the image exposure units for each color. By executing this process, the image forming device sends preset light amount correction data to a certain area in memory contained in the circuits that control driving of each image exposure unit.
Next, the image forming device determines whether or not a designation to transition to the sleep mode (hereafter, the sleep mode action transition designation) has been set in the controller of the image forming device (ST92). Until the sleep mode action transition designation has been set, the image forming device maintains a standby mode in which the printing process is immediately possible (ST92; NO). This sleep mode action transition designation is set when a print command from the host equipment, for example, is not detected within a set time. When the image forming device determines that a sleep mode action transition designation has been set as described above in the memory unit of the controller (ST92; YES), the image exposure units for each color are transitioned to sleep mode (a control action state that consumes less power than other modes) (ST93). Following this, the image forming device determines whether or not an instruction has been received canceling the sleep mode action transition designation (hereafter, referred to simply as sleep mode cancellation) (ST94). When the determination is that no sleep mode cancellation has been received, the image forming device waits for sleep mode cancellation to be ordered (ST94; No). Because the power supply to the image exposure units for each color is restricted when the switch is made to sleep mode, the light amount correction data sent to each image exposure unit as described above is extinguished.
Sleep mode cancellation is performed when a print command (input of printing data) is received from the host equipment or the like. For that reason, the image forming device upon receiving a print command determines that sleep mode cancellation has been ordered (ST94; YES) and cancels the sleep mode of the image exposure units for each color (ST95). Following this, the image forming device again sends light amount correction data to the image exposure unit for each color in order to accomplish preparatory processes for the image forming action (ST91). Following that, the printing process is accomplished in accordance with the print command.
As discussed above, an image forming device has been proposed which accomplishes a power-saving control action by reducing the power supplied to the image exposure unit when no print command is input from the host equipment within a set time.
In addition, an example of an image forming device that can further reduce power consumption in the entirety of an image forming device capable of accomplishing a plurality of types of actions, such as copy mode, print mode and scanner mode, has been disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2006-217075. This image forming device selectively supplies power needed for reading documents and power needed for writing images only with the timing necessary for copy mode, print mode and scanner mode by detecting the insertion of a document, the passing of a document or the inputting of an outside control signal.
However, the above-described conventional method for reducing power consumption in image exposure units has the following problems. In other words, in monochrome mode (black-and-white recording action), only the image exposure unit for black (K) needs to operate, so the image exposure units for color could be set to sleep mode. However, when the image exposure units for color are switched to sleep mode, the light amount correction data recorded in volatile memory in the image exposure units is lost. For that reason, with the conventional method, when canceling the sleep mode the image forming device cannot restart color mode (color recording action) without again sending the light amount correction data to the image exposure units and again storing this in the memory the image exposure units possess. In addition, when a state with no print command from the host equipment continues, the switch time condition for transitioning to sleep mode is generally set short (for example, five to 10 minutes). For this reason, with the conventional method even when the print command data sent from the superior equipment is data for a printing process in monochrome mode, ultimately the setting of the image exposure units for color to sleep mode one by one is not accomplished.
However, despite the continuance of a status under which color printing cannot be conducted, such as print jobs ordering monochrome print processes being sent multiple consecutive times from the host equipment, wasted electric power is consumed because even the image exposure units for color (not in sleep mode) are maintained in an operable condition so as to be capable of promptly responding to print jobs.
In particular, these days, when global warming should be prevented and exhaust regulations on greenhouse gases are being realized, even a small reduction in power is important. Accordingly, controlling sleep mode by distinguishing between image exposure units for color printing and image exposure units for monochrome printing in response to the recording colors of printing data input from the host equipment cannot be ignored as an effect of power-reduction policies.